Systems for performing fastening operations involving bolts and collars which are swaged on the bolts in the manufacture of large workpiece assemblies such as commercial aircraft wings are known. An example of such a system is shown in U.S. Pat. No. 5,437,094, owned by the assignee of the present invention. Such systems typically involve a tool assembly which moves along the workpiece under computer control, performing fastening operations at successive locations. A drilling tool is used to first drill a hole in the workpieces to be joined, such as a wing panel and stringer, which are typically referred to as a stackup. A die and ram assembly is used for moving a collar into position adjacent the opening, and a bolt is then positioned and moved through the opening into the collar, or alternatively, the collar is moved onto a bolt extending through the opening. The ram assembly is then operated to swage the collar onto the end tail of the bolt, completing the fastening operation. The tool assembly is then moved to the next location along the stackup.
An important part of such a system is the movement of successive collars from a storage unit, such as a bin or cartridge, to the exposed end (tail) of the bolt. In one well-known commercial system, used in many aircraft manufacturing operations, successive collars are delivered through a feed tube. In this system, the collar center opening is perpendicular to the length of the feed tube as it moves along the feed tube. The collar is fed to a gripper system, which can include spring steel fingers or other gripping arrangements. The gripper system holds the exterior surface of the collar, and transfers the collar into a position where a die pin portion of the tool assembly can engage it. The fingers or other gripper elements are opened initially to permit transfer of the collar to the gripping elements and then opened again by stripping the gripping elements away from the collar to release the collar following engagement of the die pin with the collar.
The tight clearance between the die pin and the internal diameter (ID) of the collar often results in problems in the collar transfer operation. Transfer of the collar from the feed tube to the finger assembly can result in the collar being gripped by the gripper fingers off-axis, cocked in the gripper fingers, or otherwise misaligned, preventing a good, accurate loading of the collar onto the die pin. Such misaligned collars result in loss of operation time, difficulties in swaging and poor fastening operations. Detection and removal of such misaligned collars is time consuming, expensive and requires cleanup. An accurate and reliable collar feed system for transferring the collar to the die pin axis is an important consideration in manufacturing operations involving the fastening of bolts and collars. This problem is overcome by the present system in which the collar, in particular the collar axis, is permitted a certain amount of freedom of movement relative to the die pin axis during the transfer operation.
The tight clearance between the collar ID and the bolt often results in further problems as the collar is transferred onto the bolt. Transfer of the collar from the die pin to the bolt tail can result in the collar becoming cocked on the bolt or otherwise misaligned. Misaligned collars on the bolt also result in loss of operation time, difficulties in swaging and poor fastening operations. An accurate and reliable collar alignment system with the bolt is thus important. This result is achieved in the present system by accurate, controlled movement of the collar, the die and the die pin axis relative to the extending bolt axis.
Hence, a system by which a collar can be accurately and reliably delivered onto a bolt for swaging during manufacture of large-scale mechanical assemblies, maintaining correct feed and alignment between the bolt, the collar and the moving die pin would be advantageous over existing commercial collar gripping/transfer systems. The system disclosed herein has those advantages.